Simplify the following expression: $k = \dfrac{4a - 3c}{3b - 6c} - \dfrac{6a + 6b}{3b - 6c}$ You can assume $a,b,c \neq 0$.
Solution: Since the expressions have the same denominator we simply combine the numerators: $k = \dfrac{4a - 3c - (6a + 6b)}{3b - 6c}$ $k = \dfrac{-2a - 3c - 6b}{3b - 6c}$